Appellant has raised numerous challenges to his convictions on charges of escape, conspiracy to escape, and robbery. Finding no merit in any of appellant’s contentions, we affirm the judgment of sentence.
On May 29, 1978, seven inmates, including appellant, used hooks and ropes to climb through a skylight and over a wall and escape from Holmesburg Prison in Northeast Philadelphia. Later that evening appellant and his fellow escapees robbed three men of approximately $1,000 at a tire store several blocks from the prison. The seven then fled the scene in a van which belonged to one of the robbery victims. On the morning of May 31, 1978, police discovered appellant hiding in a house in South Philadelphia, thirteen to fourteen miles from the prison, and arrested him along with four of the other escapees also found in the house. Appellant was subsequently tried jointly with five of his fellow escapees and convicted by a jury of the charges set forth above.1 Following denial of post-verdict motions and imposition of sentence, appellant took this appeal.
Appellant contends first that the evidence is insufficient to support his conviction of robbery because of deficiencies in the testimony of the only witness to identify him at trial. Specifically, appellant claims that the witness, David Scott, failed to identify him positively at trial and failed to identify him at all during a photo display conducted *5within hours after the robbery.2 The record reveals that on direct examination Scott did identify appellant as one of the robbers. Subsequently, after extensive cross-examination, Scott stated that appellant “looked like” one of the men who had robbed him, but conceded that his identification was somewhat “fuzzy” and that his recollection of the incident was fresher nearer to the time of its occurrence. In Commonwealth v. Hickman, 453 Pa. 427, 309 A.2d 564 (1973), our Supreme Court stated that “[p]roof beyond a reasonable doubt of the identity of the accused as the person who committed the crime is essential to a conviction. .. . The evidence of identification, however, needn’t be positive and certain in order to convict, although any indefiniteness and uncertainty in the identification testimony goes to its weight.” Id., 453 Pa. at 430, 309 A.2d at 566 (Citations omitted). Accord, Commonwealth v. Murray, 246 Pa.Super. 422, 429-30, 371 A.2d 910, 913 (1977) (evidence held sufficient despite witness’ concession on cross-examination that he was not “one-hundred per cent sure” of his identification of defendant). Accordingly, any uncertainty in Scott’s identification of appellant was a matter for the jury in passing on weight and credibility, and did not render the evidence insufficient to convict.3 Similarly, the fact that Scott failed to identify appellant during the photo display bears only on the weight and credibility of his trial testimony and does not undermine the conviction. See Commonwealth v. Davis, 466 *6Pa. 102, 351 A.2d 642 (1976); Commonwealth v. Tate, 229 Pa.Super. 202, 323 A.2d 188 (1974). Moreover, the lower court properly instructed the jury to receive Scott’s identification testimony with caution since it had been weakened on cross-examination. See Commonwealth v. Mouzon, 456 Pa. 230, 233-34, 318 A.2d 703, 705 (1974); Commonwealth v. Kloiber, 378 Pa. 412, 424, 106 A.2d 820, 826-27, cert. denied, 348 U.S. 875, 75 S.Ct. 112, 99 L.Ed. 688 (1954). Under these circumstances we find no merit in appellant’s challenge to the sufficiency of the evidence of robbery.
Appellant contends next that several statements which the prosecutor made during his closing argument were so prejudicial as to necessitate the grant of a new trial. In the first of these statements the prosecutor referred to an identification of appellant which Scott had made at the preliminary hearing and which was not in evidence at trial. Appellant’s objection to this statement was sustained, and the lower court carefully instructed the jury that the prosecutor’s reference to the preliminary hearing testimony was not in evidence and was to be disregarded. Subsequently, the court denied appellant’s request for a mistrial based on the statement. Appellant argues that the reference to Scott’s preliminary hearing identification of him was particularly prejudicial because it was likely to enhance the credibility of what he characterizes as Scott’s weak identification of him at trial.
Our Supreme Court has stated that “comments by the district attorney do not constitute reversible error unless the unavoidable effect of such comments would be to prejudice the jury, forming in their minds fixed bias and hostility toward the defendant so that they could not weigh the evidence objectively and render a true verdict.” Commonwealth v. McNeal, 456 Pa. 394, 400, 319 A.2d 669, 673 (1974). See also Commonwealth v. Byrd, 490 Pa. 544, 559, 417 A.2d 173, 181 (1980); Commonwealth v. Van Cliff, 483 Pa. 576, 582, 397 A.2d 1173, 1176, cert. denied, 441 U.S. 964, 99 S.Ct. 2412, 60 L.Ed.2d 1070 (1979). Here, the challenged statement was an isolated remark during the course of a trial *7which lasted more than four weeks. Moreover, the lower court immediately and succinctly cautioned the jury to disregard the statement. Under these circumstances, although it was improper for the prosecutor to refer to Scott’s pretrial identification of appellant, we do not believe that the “unavoidable effect” of the statement was to deprive appellant of an objective determination by the jury. Accordingly, the statement does not warrant granting appellant a new trial. Cf. Commonwealth v. Byrd, supra (prosecutor’s statement at close of Commonwealth’s case that there were “four other eyewitnesses” whom he would not call did not warrant new trial where statement was isolated remark during three-day trial and lower court gave sufficient cautionary instruction); Commonwealth v. Rigler, 488 Pa. 441, 412 A.2d 846 (1980) (prosecutor’s statement implying that defendant could not be trusted with an unloaded gun handed to him for identification did not warrant new trial where remark was isolated one occurring during month-long trial and lower court instructed jury to disregard prosecutor’s comment).
In the second statement to which appellant directs our attention, the prosecutor suggested to the jury that if they acquitted the defendants, they would be sending a message to the remaining inmates of Holmesburg Prison that they could escape the prison with impunity.4 This statement also provoked a motion for a mistrial, which the lower court denied. Appellant now contends that the state*8ment was intended to kindle in the jury the fear of mass escape, and hence warrants reversal.
“Although appeals to prejudice and passion are not to be approved, we have held that a District Attorney in his arguments, v/ithin proper limits, may argue for law and order and remind the jury of the danger to the community posed by persons prone to resort to violence.” Commonwealth v. Feiling, 214 Pa.Super. 207, 212, 252 A.2d 200, 203 (1969). See also Commonwealth v. Nesbitt, 276 Pa.Super. 1, 12, 419 A.2d 64, 70 (1980); Commonwealth v. Lee, 261 Pa.Super. 48, 52-53, 395 A.2d 935, 938 (1978); Commonwealth v. McHugh, 187 Pa.Super. 568, 576, 145 A.2d 896, 901 (1958). In Commonwealth v. Nesbitt, supra, this Court, faced with prosecutorial statements which were substantially more inflammatory than those here in question,5 concluded “that the lower court did not abuse its discretion in refusing to grant a mistrial.” 276 Pa.Super. at 12-13, 419 A.2d at 70. A fortiori, the prosecutor’s “message to the inmates” statement here does not warrant disturbing the judgment of the lower court.
In the final statement which appellant challenges, the prosecutor informed the jury that he would not express his opinion as to credibility or guilt because it was unethical for an attorney to do so. Then, referring to counsel for defendants, the prosecutor said, “I don’t know what law school they went to, but they should have said the same thing.” The lower court overruled appellant’s objection and subsequently denied a motion for a mistrial based on this statement. Appellant now contends that the prosecutor’s statement unfairly implied that his counsel was unethical.
*9In Commonwealth v. Nesbitt, supra, the prosecutor stated in his closing argument that defense counsel had violated the Canons of Ethics by asserting in his summation that his client was innocent. We held that although it had been improper for the prosecutor to characterize defense counsel as unethical, the impact of the prosecutor’s remark “was not so prejudicial as to require granting appellant a new trial.” 276 Pa.Super. at 11, 419 A.2d at 69. In the present case the prosecutor did not directly characterize defense counsel as being unethical; at most he did so by implication. Consequently, here, as in Nesbitt, while we do not condone the action of the prosecutor, we believe that the statement in question was not so prejudicial as to warrant reversal.
Appellant next challenges the lower court’s refusal to admit evidence of a defense to the charge of escape. At trial appellant attempted to present evidence of intolerable conditions at Holmesburg Prison, including inadequate medical care and facilities, to establish the defense of justification to the escape charge.6 Appellant asserts that this evidence would have shown that he had been suffering from several medical problems and “that desperation caused by his pain and the lack of proper medical treatment and other conditions . .. caused him to leave the prison.” Brief for Appellant at 38. The lower court ruled that evidence of such general prison conditions was inadmissible and limited any such exculpatory evidence to proof of immediate threats to the lives or personal safety of appellant and his co-defendants had they remained in prison. Appellant contends that this ruling deprived him of “a fundamental element of due process of law,” Washington v. Texas, 388 U.S. 14, 19, 87 S.Ct. 1920, 1923, 18 L.Ed.2d 1019 (1967), the right to present a defense.
*10“An accused has a fundamental right to present defensive evidence so long as such evidence is relevant and not excluded by an established evidentiary rule.” Commonwealth v. Greene, 469 Pa. 399, 404, 366 A.2d 234, 237 (1976). See also Commonwealth v. Boyle, 470 Pa. 343, 368 A.2d 661 (1977); Commonwealth v. Bailey, 450 Pa. 201, 299 A.2d 298 (1973); Commonwealth v. Collins, 447 Pa. 300, 290 A.2d 121 (1972). In Commonwealth v. Clark, 287 Pa.Super. 13, 429 A.2d 695, also decided on this day, one of appellant’s co-defendants contended that the lower court had erred in disallowing the same evidence of adverse prison conditions to establish the defenses of duress and/or justification as appellant had sought to introduce to establish justification only. We held there that “because generally adverse prison conditions do not constitute a defense to a charge of escape and because appellant did not offer to prove an effort or intention to surrender to authorities after his escape, the lower court properly refused appellant’s proffered evidence of conditions at Holmesburg Prison.” At 695 (footnote omitted). Our analysis of the claim set forth in Clark is entirely applicable to appellant’s claim, and, accordingly, we will not repeat it here. It is sufficient to say that for the reasons expressed in Clark, appellant’s proffered evidence was inadmissible to establish the defense of justification, and thus, the lower court’s exclusion of that evidence did not deprive appellant of his fundamental right to present a defense in his behalf.7
*11Appellant contends next that the lower court erred in refusing his requested jury instructions on the effect of prior inconsistent statements on the credibility of witnesses. At trial all three robbery victims testified that they had been robbed by seven men wearing blue pants resembling those later found near the tire store and identified as prison pants. Cross-examination revealed, however, that in pretrial statements (including statements taken shortly after the incident) the three victims had given varying estimates of the number of perpetrators (ranging from six to nine), and had not always provided descriptions of their assailants’ clothing. Appellant argues that these inconsistencies had such a critical bearing on the witnesses’ credibility that the failure to give the requested instruction constitutes reversible error. We disagree. It is settled that “the trial court is not required to accept the language of the point submitted by counsel but rather is free to select its own form of expression. The only issue is whether the area is adequately, accurately and clearly presented to the jury for consideration.” Commonwealth v. McComb, 462 Pa. 504, 509, 341 A.2d 496, 498 (1975). We have reviewed the general instructions of the court and conclude that they were sufficient to alert the jury to consider the effect of inconsistencies in the witnesses’ statements on their credibility. Accordingly, we find no error in the court’s refusal to give further instructions on the subject.8
*12Appellant contends finally that he was denied due process of law and equal protection of law by the lower court’s use of what he asserts is a less favorable jury instruction on the meaning of the term “reasonable doubt” than that which he requested. Appellant requested the court to instruct the jury that “[a] reasonable doubt is a doubt that would cause a reasonably careful and sensible person to hesitate before acting upon a matter of importance in his own affairs” (emphasis added). The court denied this request and instructed the jury that “[t]he law has defined a reasonable doubt as that doubt that will restrain a reasonable, careful and sensible person from acting upon a matter of the highest importance in his own affairs” (emphasis added). Our Supreme Court has expressly approved both of these definitions for use in jury instructions. See Commonwealth v. Young, 456 Pa. 102, 317 A.2d 258 (1974), and cases cited therein. Appellant contends, however, that the “hesitate” version which he requested allows the jury to acquit on a lesser quantum of doubt than does the “restrain” version which the court employed. Consequently, appellant claims that he was denied due process and equal protection by the fact that the trial judge was free arbitrarily to choose to use the less favorable definition in his instructions. We disagree. That the “hesitate” version is more favorable to defendants than the “restrain” version is by no means certain.9 Indeed, the fact that our *13Supreme Court has approved both versions of the instruction indicates its belief that the difference, if any, is inconsequential. Accordingly, we infer from the Supreme Court’s approval of both definitions that appellant’s constitutional rights were not infringed by the lower court’s freedom to employ the “restrain” version in its jury instructions.